Radiopaque fluorocarbons (RFC) are new compounds in diagnostic radiology, and these compounds have unique and valuable characteristics that are not shared with other radiologic contrast agents. The RFC's are chemically stable and biologically inert and safe. Because of their low surface tension and low viscosity, fluorocarbon liquids coat surfaces readily and rapidly. Ongoing human studies and animal experiments have proved that RFC's are safe and effective in diagnostic radiology of the lungs and gastrointestinal tract. Experiments with RFC in lymphography have been completed and humans studies will be started soon. Emulsions of RFC have been perfected so that large quantities can be given safely intravenously. Preliminary studies show that small particle size emulsions radiopacify the entire cardiovascular system for several hours after injection. The emulsions are phagocytized by the reticulo-endothelial cells of the spleen and liver, thus providing excellent radiodensity of these structures. The adrenal glands, myocardium and, to a lesser extent, the ovaries become radiodense at different times after dosing. Radiopacification of experimental malignant tumors also occurs following the intravenous injection of RFC. Theoretically, RFC should be ideal for enhancement of computed tomography (CT) of the body. Emulsions of RFC will be evaluated as a radiographic diagnostic agent following intravenous administration. We will employ routine X-ray techniques and CT of the body as well as specific organ tomography and tumor site tomography. Experiments will be designed to develop the optimum safe dosage of RFC as well as the timing of X-rays and CT of specific organs and tumors. Transplanted, induced and spontaneous tumors will be used. Radiologic diagnosis of myocardial infarction will be studied in dogs with coronary occlusion. The safety of RFC emulsions will be examined by hematologic as well as serologic studies. Effects on the immune system will be examined by studies of immune globulins and skin graft rejection. The biologic disposition of RFC will be documented by gas chromatographic analysis of tissue extracts. Light and electron microscopic studies will be used to determine cellular disposition and toxicity of RFC.